SEPT/OCT, 1997

RED CELL TRANSFUSION THERAPY

Ileana Lopez-Plaza, M.D.

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INTRODUCTION

Over ten million units of red cells are transfused annually in the US. Red cell transfusion remains an important part of blood component therapy both in adult and pediatric, medical and surgical patients. Understanding its uses and alternatives will contribute to optimal patient care and minimization of health care costs.

DESCRIPTION

A unit of packed red cells (RBC) comes from a unit of whole blood which has been separated into blood components by centrifugation. The packed red cell final volume, hematocrit, and shelf life is dependent on the anticoagulant/preservative used.

COMPATIBILITY

Only ABO identical or compatible RBC can be transfused (Table 2). Rh negative recipients should be transfused with Rh negative RBC. A sample is required every three days in transfused patients to ensure compatibility. Patients with red cell antibodies require special red cells which lack the corresponding antigens. Coordination with the blood bank is required for these components. Only 0.9% sodium chloride solution can be added to a red cell component bag.

One unit of packed RBC increases the hemoglobin by 1g/dL and the hematocrit by 3 percentage points in an adult. In infants a dose of 10 mL/Kg will increase the hematocrit by 8-10 percentage points. Post transfusion hemoglobin levels performed as early as 15 minutes after transfusion in most cases provides an adequate assessment of the response to the transfusion.

INDICATIONS

The transfusion of red cells is indicated for correcting oxygen carrying capacity in patients with symptomatic anemia. One of the most accurate way of determining tissue oxygenation is by measuring the arterial/venous oxygen gradient, a measurement limited to OR and ICU patients. In every day clinical practice the hemoglobin/hematocrit level is the most common indicator used for the need for red cell transfusion. However, these values only provide an estimate of the oxygen carrying capacity and do not assess tissue oxygenation. Therefore, it is recommended that a clinical assessment (symptoms and signs of anemia) of the patient along with the hemoglobin/hematocrit measurements be used to assess the need for red cell transfusion. Prior to transfusion the cause of the anemia should be determined, and alternative therapeutic interventions should be considered, including the used of bed rest and supplemental oxygen.

Red cell transfusion should be considered in the following situations:

• HGB/HCT < 7g/dL /21% in a hemodynamically stable patient without significant cardiovascular disease.

• HGB/HCT < 8g/dL/24% in a patient with significant cardiovascular disease or hemodynamic instability.

• A patient with acute blood loss (15-20% blood volume or 750-1000 mL) associated with hemodynamic instability.

Contraindications to red cell transfusion:

• Volume expansion when oxygen carrying capacity is adequate.

• To enhance the general sense of well being.

• To promote wound healing.

• Prophylactically, in the absence of symptomatic anemia.

COMPLICATIONS / RISKS

Fever-chill reactions occur in 0.5-1 % of red cell transfusions. These reactions occur due to white cells contaminating the red cell component. The reaction can be prevented by the use of antipyretics prior to transfusion and/or by using leukoreduced(filtered) red cell components. Allergic reactions occur in 1% of red cell transfusions. These reactions are generally mild and easily treated or prevented with antihistamines. Circulatory overload also occurs but can be managed by controlling the volume and rate of administration.

Rare reactions to red cells include: septic reactions due to bacterial contamination, graft versus host disease, and ARDS (transfusion related acute lung injury).

The potassium load in red cells is rarely of clinical concern requiring intervention only in patients with preexisting hyperkalemia associated with renal failure.

The current risks of viral transmission from a unit of blood are shown in Table 3.

* U.S. risks from Schreiber GB et al. NEJM 1996;334:1685

** Risks based on Central Blood Bank donor prevalence statistics

SPECIALIZED RED CELL COMPONENTS

[ NOTE: Consultation with the Blood Bank prior to ordering is recommended ]

Leukoreduced:  Leukocyte content is reduced by filtration; indicated for the prevention of recurrent febrile reactions, the prevention of HLA alloimmunization or the prevention of CMV transmission.

Irradiated: Gamma irradiation (2500 rads) is used to prevent transfusion associated graft versus host disease from lymphocytes in the blood component. Indicated for patients at risk for GVHD i.e. stem cell transplant recipients. Directed blood from blood relatives should also be irradiated.

CMV Seronegative: A unit that tests negative for CMV antibodies. Indicated for selected CMV negative patients at risk for CMV disease.

CMV Safe: A unit with reduced CMV infectivity by removing white cells by filtration. It is considered an acceptable substitute for CMV seronegative red cells.

Washed: > 90% of plasma content is removed by using an automated saline wash procedure; washing time is 60 minutes; used to prevent severe allergic reactions not controlled by medications.

Frozen/Deglycerolized: Mostly units with rare red cell phenotypes for patients with multiple antibodies. Requires 3 hours of preparation for transfusion.

FUTURE CONSIDERATIONS

Phase III clinical trials are underway evaluating the efficacy of red cell substitutes (hemoglobin solutions) in both trauma victims and surgical patients. No FDA approved red cell substitutes are currently available.

Copyright © 1997, Institute For Transfusion Medicine